Thanks for the tips on the mesh guys, I will check them out.
So, you get far in and then find something that radically changes everything you've done and now you suddenly realise that the whole thing may not work.
I'd assumed that the angle of the hull was a constant line. But over hours trawling the net I've discovered images of M551 hulls that show the lines of the forward hull going in unexpected directions. So it's out with the Verniers tonight to see if I can make the hull work after all.
Here's the images that threw said cat among said pigeons.